Precharge circuit

A precharge circuit having step-up node means including a capacitor for supplying a drive voltage having a predetermined level, for raising said drive voltage to a stepped-up voltage level which is greater by a specific value than said predetermined level and for delivering said drive voltage at said predetermined level or at said stepped-up voltage level to a load, said precharge circuit comprising:

• main transistor means comprising a main P-channel metal oxide semiconductor (MOS) transistor having a gate terminal, a source terminal, a drain terminal and a substrate terminal;
• subsidiary transistor means comprising a subsidiary P-channel metal oxide semiconductor (MOS) transistor having a gate terminal, a source terminal, a drain terminal and a substrate terminal;
• means for connecting said drain terminal of said subsidiary transistor to said gate terminal of said main transistor;
• means for connecting said source terminal of said main transistor to a positive potential power supply;
• means for supplying a first input signal to said gate terminal of said subsidiary transistor;
• and
• means for supplying said drive voltage to said source and substrate terminals of said subsidiary transistor;
• said main transistor means providing said drive voltage at said predetermined level for delivery to said load through said step-up node means when a step-up input signal at ground level is input to said step-up node means;
• said subsidiary transistor means turning on, due to said drive voltage being raised by said step-up input signal, immediately before said drive voltage exceeds said predetermined value and turning off due to said gate of said subsidiary transistor being input with a voltage level which is the same level as said drive voltage.